Let me join in and support "hdm" and "Psychicanimal" sagacious advice. A 7" 45 RPM record dance record with lots of octave divided synthesized bass is GREAT for break-in because 45's are cut 12dB hotter than LPs. I do not know if 45 EPs are cut hotter as well or not. After 10-15 hours you will know basically what you have and between there and 50-60 hours it just gets better - kind of "warms up".
For cartridge matching please see my old primer article on 6 Moons Audio (I think that it is still there?). The DCR is 40 Ohms and the impedance is well .. who knows... cartridge impedance is a misnomer. The 100 Ohm load thing is just a convenient guess, or starting point, provided by the manufacturer. The overall electrical system is too complex for any absolutes - it all MUST be derived empirically.
My advice? No? Well I'll give it anyway... eventually try to forget active (head amp) and go with transformers for MC step-up! The UTC A-11 based box I built for Jeff Day's Denon 103D or the Altec 4722 sound simply wonderful with the 103R,D,S, etc. series.
Active's are nice at being flexible for a wide range of cartridges but a good transformer is far superior at really hearing the cartridge.
The DENON MC cartridges are absolutely a bargain! Even in today's market! Yes, they have their foibles and limitations but they definitely provide "most bang for the buck!" OTOH, they just might get you hooked on MC cartridges. ;^)